I started with this wooden drag. It actually did a pretty good job of packing the snow, but as the snow piled up it couldn't level the trail or renovate the old snow. I still have this drag and use it early in the season to pack down the first couple of snow falls. It's also handy for hauling firewood or ice fishing supplies.
The picture on the left shows the tarp (rolled up) that would normally cover the drag. While grooming, the drag fills up with snow which adds weight and helps pack the trail. To lighten the drag for deep snow or hills, I just grab the tarp and flip the snow off.
The picture on the right shows the grooves I routered in the bottom of the drag to leave a "combed" finish on the trail.